Preheat the oven to 350 degrees and line two cookie sheets with parchment paper. In a medium bowl combine flour, cocoa powder, baking soda, cornstarch, salt, and instant coffee granules until well mixed. Set aside.
In the bowl of your stand mixer (or a large bowl with a hand mixer) beat butter and both sugars until light and fluffy, 3-5 minutes. Beat in egg and egg yolk until fully incorporated, followed by the vanilla.
On the lowest setting of your mixer, stir in the flour mixture until dough forms.
Scoop out rounded tablespoons of dough and place at least 2 inches apart on prepared cookie sheets. Use the bottom of a drinking glass coated with cocoa powder to gently flatten cookies (just a bit!).
Bake at 350 degrees for 12-14 minutes or until edges just begin to brown. Remove from oven and immediately push (gently!) a caramel kiss into the center of each cookie. Sprinkle tops of cookies with sea salt.
Let cool on pan for 3-4 minutes before gently removing to a wire rack to cool completely.